Barrels won't come off.

[B. Dudley]

Not ALL guns will fully expose the hook screw when the breech is open.

If you try this route, tread carefully.

[edgarspencer]

Whether you're able to gain sufficient access to the screw or not, removing the barrels this way only gets the barrels off, but doesn't correct the problem, which as Brian says, is more than likely that the cocking slide is not coming all the way back, for a variety of reasons. The most likely is old congealed grease or crud.

[J. A. EARLY]

Originally Posted by Brian Dudley

Not ALL guns will fully expose the hook screw when the breech is open.

It seems to work on 9 out of 10 twelve gauges. It does not work on sixteen and smaller from samples I've tried. It is best a two person job since you have to exert extra opening pressure for the screw to clear the frame.

Then you may be able to put some penetrating oil on the offending part.